1. Field of the Invention
This invention generally relates to an electromagnetic energized microwave oven wherein the food is heated or cooked by transmitting a microwave from a magnetron to the heating room, and more particularly to a microwave leakage shielding apparatus of microwave oven wherein the serial resonant circuit is provided in the attenuating cavity of the choke in a door installed at the front of the microwave oven in order to cut off the leakage of microwave or high-frequency electromagnetic energy.
2. Description of the Related Art
The conventional microwave oven generally cooks or heats the food by using a high-frequency wave of 915 or 2450 megahertz. In most of the recent microwave ovens, the high-frequency wave of 2450 megahertz is being used.
In the cooking or heating of food by utilizing such high-frequency waves, it is very dangerous for the human to receive more than the order of 100 mw/cm.sup.2 in his body, due to the leakage of such a high-frequency electromagnetic energy to the exterior of the microwave oven. Therefore, all countries of the world are restricting the leakage amounts of high-frequency electromagnetic energy to be less than the order of 5 mw/cm.sup.2 a distance of 5 cm from the door at the worst state and are producing the microwave oven to be less than the order of 1 mw/cm.sup.2. However, there developed a serious problem in that the high-frequency wave may leak through the gap between the door and the main body of the microwave oven caused by the release of a door hinge, etc. during the use thereof, or the gap between the door and the heating room caused by filth or remnants of food and the like, thereby causing human body harm.
In order to prevent the high-frequency wave from leaking through such gaps generated during the use of the oven, U.S. Pat. No. 2,500,676 suggests to shield the leakage of microwave energy by a metal-to-metal contact or the metallic contact between the door and the heating room. However, this suggestion has been found to have shortcomings in that the metal-to-metal contact is formed by a local point-contact, so that leakage of microwave energy is increased in proportion to the use time of products.
Further, U.S. Pat. No. 3,182,164 suggest to shield the leakage of microwave energy by utilizing the impedance inversion of .lambda./4 (herein, .lambda. is a wavelength of microwave). This has been found to have shortcomings in that the length for performing the ideal inversion is approximately the order of 32 mm in the microwave oven using a high-frequency wave of 2450 megahertz, and accordingly the thickness of the door becomes greater, so that it is very difficult to minimize the size of the products and lighten the weight thereof.